This invention relates to a process for manufacturing macroreticular crosslinked copolymer particles, wherein the resulting copolymers are substantially consistent from batch to batch in pore size and porosity. These copolymer particles are capable of being converted into ion exchange resins.
Polymeric ion exchange resins in the form of spheroidal beads are used in many applications as chelating resins and as anion or cation exchangers. Of particular interest are those resins prepared from macroporous copolymer particles (i.e., copolymer particles having a macroreticular character). Such copolymer particles are typically prepared by suspending a suspension polymerizable monomer and crosslinking agent in a reaction medium in the presence of a diluent in which the monomers are soluble, but the copolymer prepared therefrom is not. During polymerization, the copolymers phase separate and agglomerate from the diluent phase. Thus, spaces or channels left between the precipitated copolymer agglomerates form the pores of the macroporous particles. The diluent which can remain in the pores of the copolymer particle is typically removed by techniques such as steam distillation.
In commercial processes, after the macroporous copolymer particles are polymerized and separated from the diluent, the diluent is recycled. The problem with the prior art is that the quality of the macroporous copolymer particles varies a great deal. Therefore, it would be highly desirable to provide a process for preparing copolymer particles having a macroreticular character, which process is capable of producing copolymer particles that exhibit high quality consistently.
Contrastingly from these commercial processes, we have discovered that as recycled diluent is employed in the preparation of further amounts of macroporous copolymer particles, the diluent may become contaminated. We have also discovered that this change in diluent purity can result in the preparation of macroporous copolymer particles which exhibit significant differences in particle porosity.